Bell-jar vacuum evaporator



Jam 3L H0 c. N. HOYLER EWM BELL JAR VACUUM EVAPORATOR Filed July 27,1945 ATTORNEY.

Patented Jan. 31," 1950 BELL-JAR VACUUM EvAroRA'roR Cyril N. Hoyler,Princeton, N. J., assgnor to Radio Corporation of America, a corporationof Delai Ware Application July 27, 1945, Serial No. 607,410

This invention relates to vacuum apparatus for the treatment ofmaterials, and particularly to improvements in evaporators.

In the dehydration or concentration by evapo ration of certainmaterials, notably biological and pharmaceutical products, it is usuallynecessary or desirable to maintain the dome or cover of the evaporatorat an elevated temperature in order to prevent the vaporous emanationsof thel uid from condensing and. dropping back into the batch or ontothe base or hot plate of the evaporator. To this end, it has beenpreviously proposed to provide an auxiliary device such, forexample, asan externally mounted infra-red lamp, for heating the hood or othersurface of the evaporator upon which the undesired condensation islikely to occur. Obviously, such auxiliary equipment adds to the costand complicates the operation of the evaporator. Furthermore, theradiant heat supplied by the auxiliary heater may afect the comfort ofthe operator and the life of the rubber or other gasket employed informing the air-tight seal about the hood or cover.

Accordingly, the principal object of the present invention is to obviatethe foregoing objections to present day vacuum apparatus and, morespecifically, to provide an improved dehydrator or evaporator whereincondensation is prevented without the use of any auxiliary heatingequipment.

The foregoing and other objects are achieved in accordance with theinvention by the provision of an external gasket or seal of novelconstruction and which permits the removable hood or other closureelement of the evaporator to be mounted in direct heat transfer relationwith the heated inner surface or base upon which the material to betreated is mounted.

Certain preferred details of construction together with other objectsand advantages will be apparent and the invention itself will be bestunderstood upon reference to the following speciiication and to theaccompanying drawing where- Figure l is an elevational view, partly insection, of an evacuable chamber incorporating the invention, and

Figure 2 is a plan view, with the cover removed, of the device of Fig.l.

In the embodiment of the invention which has been selected forillustration, l designates, generally, an evacuable chamber comprising aheated metal platform or base 3 and a closure element or cover which, inthe instant case, is in the form of a removable metal bel1-jar or hood.5. Any

4 Claims. (Cl. 159-29) suitable means, such, for example, as anelectrical resistance unit 'l which may be mounted on or in the base 3is provided for heating the chamber l and hence the material to betreated therein. Where the material to be dehydrated comprises a drug indosage quantities, the drug ampoules 9 may be contained in rack i Iwhich is simply laid on the heated inner surface 3a of the base. Thespace within the chamber I is evacuated through a port I3 in themetal-base 3 and is connected to a suitable vacuum pump :grot shown)through a water cooled condenser Since the hood or cover 5 presents arelatively large surface to the ambient it is apparent that, unless thecover is heated, the vapors which emanate from the material beingtreated may condense upon its inner surface and drop back into theampoules 9 or onto the heated innersurface of the base 3. As previouslyindicated, in order to prevent such undesired condensation, the presentinvention dictates the heating of the cover 5 with energy supplied byconduction from the heated base 3. Such a direct connection is madepractical by the provision of a gasket-seal of novel constructionarranged preferably on the exterior of the evacuable chamber I adjacentto and surrounding the said direct heat-exchange connection.

In carrying the invention into eiect the diameter of the base 3 is madesubstantially larger than the diameter of the hood or cover 5 and ispreferably provided with a circumferential rim 3b so that there is acircular channel or groove 3c between the cover 5 and the rim 3b whenthe cover is closed. An endless piece of rubber or similar iexiblepneumatic tubing l'i is preferably cemented as indicated at ila in thegroove or channel 3c adjacent to the rim 3b. A circular projection i9 onthe outer surface of the hood 5 is arranged preferably somewhat belowthe level of the rim 3c. Thus when the hood is brought down over thebase 3 the circular projection i9 merely rests upon the flexible memberl1 without collapsing it. However when the chamber I is put on the pumpthe pressure of the atmosphere upon the hood is transmitted through theprojection lil to the gasket Il which is thereby partially collapsed ordistorted and forms a vacuum tight seal about the said chamber. Thepressure of the atmosphere on the hood 5 is carried by the base when thetubing l'! is collapsed sufliciently to cause the hood to become seatedon the base in order to establish the desired direct heat conductiveconnection between the base and the hood 5. Since the weight of the hood5 and the pressure of the atmosphere thereon is borne principally by themetal base 3, and not by the gasket alone, the yieldable member l'l maybe used repeatedly without impairing its usefulness.

It will now be apparent that the present invention provides an improvedevaporator and one wherein condensation of the vapors is preventedwithout the use of any expensive or troublesome auxiliary equipment.

What is claimed is:

1. Apparatus for the dehydration of materials comprising a base providedwith an inner surface, means for heating said surface, a closure elementhaving an inner surface normally exposed to the vapors from saidmaterial and upon which said vapors may condense in the absence of heat,said closure element being adapted to be moved into direct heat exchangerelation with said heated surface whereby to heat said closure elementand thereby prevent the condensation of said vapors thereon, acompressible gasket containing entrapped air supported exterior of theperiphery of said closure element, and means on said closure elementresponsive to said movement of said closure element for applying acompression force to said gasket whereby to establish an air-tight sealabout said surfaces.

2. The invention as set forth in claim 1 and wherein means are providedfor evacuating said casing whereby said downward movement of saidclosure element and the formation of said airtight seal between saidheated surface and said closure element results from the operation ofsaid casing-evacuating means.

3. Apparatus for the dehydration 0f materials comprising a heatablebase, means to heat said base, a removable hood having a lower open-endadapted to be seated on said base and having an inner surface normallyexposed to hot vapors from said material and upon which said hot vaporsmay condense when said hood is cold, a projection on the outer surfaceof said hood adjacent to its said lower end, a pneumatic tube on saidbase about the outer periphery of said hood and upon which saidprojection is adapted to rest to (normally support said hood out ofcontact with the base, and means for evacuating air and moisture fromthe interior of the apparatus whereby atmospheric pressure upon saidhood will cause it to move downwardly into direct heat transferrelationship with the base and cause said projection to compress saidtube to form an air-tight seal between the hood and base.

4. Apparatus for the treatment of materials comprising a base, means forheating said base, a removable hood constituted of heat conductivematerial and having an open end adapted to be mounted upon said basewith the edge of the hood in direct heat exchange relation with saidbase, a pneumatic tube on said base adjacent to the outer periphery ofsaid hood, and a projection on the outer surface 0f said hood forengaging and compressing said pneumatic tube when said hood is mountedupon said base.

CYRIL N. HOYLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 499,486 Walter June 13, 18932,263,008 McRae Nov. 18, 1941 2,271,239 Vokes Jan. 27, 1942 2,302,253Reichel et al Nov. 17, 19412 2,338,234 Dimmick Jan. 4, 1944 FOREIGNPATENTS Number Country Date 40,532 Australia Jan. 10, 1910

